Preparation of substituted aldehydes



monopropyl, ethers of ethylene glycol, while the aryloxy acet- Patented June 9, 1942 UNITED STATES. PATENT OFFICE 2,286,034

PREPARATION OF SUBSTITUTED mamas William F. Gresham, Wilmington, Del., assignor to E. I. du Pont de Nemours & Company, Wilmington, Del, a corporation oi Delaware No Drawing. Application April 4, 1939, Serial No. 265,969

2 Claims.

isopropoxy acetaldehyde, CH2(OC3H1) CHO; butoxy and ixobutoxy acetaldehyde,

CH2(OC4H9) CHO and higher homologues thereof, as well as phenoxy acetaldehyde, CH2(OC6H5) CH; andbenzoxy acetaldehyde, CHz(OCHgCeH) CH0, and the acyloxy acetaldehydes such as, acetoxy acetaldehyde, CHaCOOCHzCHO. The oxy-substituted aldehydes of the invention are prepared from corresponding monoalkyl, monoalkoxy alkyl, and monoaryl ethers of ethylene glycol. Accordingly, the alkoxy acetaldehydes above designated may be prepared, respectively, from the monomethyl, monomethoxy methyl, monoethyl, monobutyl, and monoisobutyl aldehydes may be prepared, respectively, from the monophenyl ether and the monobenzyl ether of ethylene glycol and acetoxy acetaldehyde from glycol monoacetate,

(CH3COOCI-I2.CH2OH).

An object of the present invention is to provide a process 101 the preparation of the above designated oily-substituted acetaidehydes. Another object ofthe invention is to provide a process for the preparation 01' alkoxy and aryloxy acetaldehydes by the dehydrogenation of monoalkyl or monoaryl ethers of ethylene glycol. Another object of the invention is to provide suitable catalysts and conditions under which the process may be carried out. Other objects and advantages of the inviention will hereinatter appear.

The process of the invention may be conducted by passing a vaporized ether of ethylene glycol, preferably in the presence 01' an inert diluent. over a dehydrogenation catalyst in accord with the equation:

onion nil-onion HaOH HO in which R is an alkyl group such, for example,

as methyl, ethyl propyl, isopropyl, butyl, isobutyl, amyl and higher alkyl groups; an alkoxy alkyl group such as methoxy methyl, ethoxy methyl, propoxy methyl, etc., an aryl group such as phenyl, benzyl and the like, or a phenoxy alkyl group such as phenoxy methyl. The reaction is conducted in the presence of a suitable dehydro genation catalyst at temperaturesranging between 200 and 375 C. with a preferred temperature ranging between 250 and 325 C. Pres sures between 5 and 1000 atmospheres may be employed although the reaction will proceed at a favorable rate under pressures in the neighborhood of atmospheric. 4

Dehydrogenation catalysts which are suitable for conducting this reaction may be obtained by fusing copper oxide alone or in conjunction with another metal oxide such, for example, as magnesium oxide, nickel oxide or the likeand subsequently reducing theresulting fusion of metals. The catalysts oi. this type aremore fully described in the copending application of A. T. Larson, S. N. 171,894, filed October 30, 1937. Copper and nickel bearing catalysts may likewise be usedas well as copper-nickel and coppersilicon catalysts prepared b Precipitation of a 'mixture of their salts followed by reduction.

Copper zinc chromate catalysts similarly prepared may also be used as well as fused and reduced mixtures of copper oxide and zinc oxide.

Straight nickel catalysts or nickel catalysts prometed with cerium may be used but, due to their more powerful catalytic eflectiveness very mild conditions should be employed to prevent conversion to hydrocarbons. A very effective catalyst for the dehydrogenation can be prepared by tusing a mixture of copper oxide, (CuO) silicon dioxide (810:) and chromium oxide (mm) in a preferred molal ratio of :1025, the i'used mixture is reduced and, after cooling, cmshed to a suitable size prior to use. Other suitable dehydrogenation catalysts may be used.

It has been ifound advantageous to conduct the reaction in the presence or water vapor or other inert diluent such as nitrogen and carbon dioxide, and it .is desirable to maintain, on a mole] basis, the ratio of water vapor (or other diluent) to the glycol ether at approximately 0.4 mol thereof per moi of the ether. Without the use of diluents, dehydrogenation catalysts generally lose their initial activity very rapidly.

The more detailed practice of the invention is illustrated by the following examples in which parts given are by weight unless otherwise stated.

There are, of course, many forms of the invention other than these specific embodiments.

Example 1.An equimolar mixture of monomethyl ether of ethylene glycol and water was passed into a catalyst chamberelectrically heated to a temperature between. 250 and 260 C. The chamber was charged with a metal catalyst prepared by fusing a mixture containing 100 mols of copper oxide, .10 mols of silica and 5 mols-of chromium oxide, (CrOs). The resulting fused catalyst wascrushed to 8 to 14 mesh size and then reduced in an atmosphere of hydrogen at approximately 300 C. Priorv to direct contact with the catalyst the glycol etherwater mixture was preheated to substantially reaction temperature, and, after passing through the reaction zone (at a space velocity of 3000-- 1000 based on water plus glycol ether), the reaction product, which consisted essentially of methoxy acetaldehyde and water, was condensed. Upon fractionation an approximately 40% yield of methoxy acetaldehyde was obtained.

Example 2.-An equimolar mixture of glycol methyl ether and water was vaporized over a catalyst, (prepared as described in Example 1 from 100 mols of copper oxide, 50 mols of silica and 10 mols of chromic oxide) at 300 C. v and a total space velocity of 4000. The product porlzed over the copper-silica-chromium catalyst described in Example 1 at 280-290 C. and a space velocityof 1500. The reaction product was condensed and fractionally distilled. Meth-- oxymethoxyacetaldehyde (b. p. 135-138 C.) was obtained.

Example 5.The process of Example 2 was repeated using glycol monoacetate and a fused metal catalyst which, prior to fusion; had the composition, copper oxide (CuO), 100 mols; silicon dioxide (SiOz), l0 mols; and chromium oxide (Cr03), 5 mols. The reaction was conducted at approximately 290 C. and acetoxy acetaldehyde (boiling point 90 C. at 50 mm.)

recovered from the reaction products by distillation.

From a consideration of the above specification it will be realized that many changes may be made in the details therein given without departing from the scope of the invention or sacrificing any of the advantages that may be derived therefrom.

I claim:

1. A process for the preparation of methoxy. acetaldehyde which comprises dehydrogenating monomethyl ether of ethylene glycol at a temperature between 200 and 375 C., in the pres-"- ence of water vapor using a fused and reduced metal oxide catalyst containing copper oxide, silicon dioxide and chromium oxide in the molal ratio prior to fusion of 100:1025.

2. A process for the preparation of methoxy acetaldehyde which comprises introducing an equimolar mixture of .water and monomethyl ether of ethylene glycol into a reaction zone containing a fused and reduced copper-siliconchromium catalyst, maintaining the reaction zone at a temperature between 250 and 325 0.,

condensing the reaction product and recovering therefrom methoxy acetaldehyde.

WILLIAM F. GRESHAM. 

